This invention generally relates to techniques for optical switching. More particularly, the present invention provides a device having a novel mirror configuration, which integrates a mirror array with an integrated circuit. Merely by way of example, the present invention is implemented using such device in a wide area network for long haul telecommunications, but it would be recognized that the invention has a much broader range of applicability. The invention can be applied to other types of networks including local area networks, enterprise networks, and the like.
Digital telephone has progressed with the need for faster communication networks. Conventionally, standard analog voice telephone signals have been converted into digital signals. These signals can be 64,000 bits/second and greater in some applications. Other telephone circuits interleave these bit streams from 24 digitized phone lines into a single sequence of 1.5 Mbit/second, commonly called the T1 or DS1 rate. The T1 rate feeds into higher rates such as T2 and T3. A T4 may also be used. Single mode fiber optics have also been used at much higher speeds of data transfer. Here, optical switching networks have also been improved. An example of such optical switching standard is called the Synchronous Optical Network (SONET), which is a switching standard designed for telecommunications to use transmission capacity more efficiently than the conventional digital telephone hierarchy, which was noted above. SONET organizes data into 810-byte xe2x80x9cframesxe2x80x9d that include data on signal routing and designation as well as the signal itself. The frames can be switched individually without breaking the signal up into its components, but still require conventional switching devices.
Most of the conventional switching devices require the need to convert optical signals from a first source into electric signals for switching such optical signals over a communication network. Once the electric signals have been switched, they are converted back into optical signals for transmission over the network. As merely an example, a product called the SN 16000, BroadLeaf(trademark) Network Operating System (NOS), made by Sycamore Networks, Inc. uses such electrical switching technique. Numerous limitations exist with such conventional electrical switching technique. For example, such electrical switching often requires a lot of complex electronic devices, which make the device difficult to scale. Additionally, such electronic devices become prone to failure, thereby influencing reliability of the network. The switch is also slow and is only as fast as the electrical devices. Accordingly, techniques for switching optical signals using a purely optical technology have been proposed. Such technology can use a wave guide approach for switching optical signals. Unfortunately, such technology has been difficult to scale and to build commercial devices.
Other companies have also been attempting to develop technologies for switching high number of signals in other manners such as high density mirror arrays, but have been generally unsuccessful. One of the major obstacles to manufacturing high-density mirror arrays is the sheer number of interconnects that must come out of the mirrors for control and sensing. Another issue that arises is that since the mirrors are so small the capacitance values (fempto-farads) that one uses to sense the mirror position are equally as small that if one tries to sense the capacitance xe2x80x9coff-chipxe2x80x9d the signal is buried in the noise of the stray capacitance from the interconnects. Accordingly, such attempts have been unsuccessful.
From the above, it is seen that an improved way to switching a plurality of optical signal is highly desirable.
According to the present invention, a technique including a device for optical switching is provided. More particularly, the invention provides an integrated circuit and mirror device. Merely by way of example, the present invention is implemented using such a device in a wide area network for long haul telecommunications, but it would be recognized that the invention has a much broader range of applicability. The invention can be applied to other types of networks including local area networks, enterprise networks, and the like.
In a specific embodiment, the present invention provides an integrated circuit and mirror device. The device includes a first substrate comprising a plurality of electrode groups, wherein each of the groups comprises a plurality of electrodes. A mirror array is formed on a second substrate. Each of the mirrors on the array has a mirror surface being able to pivot about a point (e.g., fixed point, region) in space. Each of the mirrors has a backside surface operably coupled to one of the electrode groups. A bonding layer mechanically couples the first substrate to the second substrate, whereupon the backside surface of each mirror faces one of the electrode groups. The device also has a drive circuitry coupled to each electrode groups. The drive circuitry is configured to apply a voltage to any one of the electrodes in each of the electrode groups. The drive circuitry is disposed in the first substrate and is adapted to pivot each of the mirror faces about the point in space to reflect optical signals.
In an alternative embodiment, the invention provides an integrated circuit and mirror device. The device has a first substrate bonded to a second substrate. The first substrate has a plurality of electrode groups disposed in a spatial manner, where each of the groups comprises a plurality of electrodes. A mirror array is formed on the second substrate. Each of the mirrors on the array has a mirror surface being able to pivot about a point (e.g., fixed, region) in space. Each of the mirrors also has a backside surface operably coupled to one of the electrode groups. A bonding layer mechanically couples the first substrate to the second substrate, whereupon the backside surface of each mirror faces one of the electrode groups. A drive circuitry is coupled to each electrode groups. The drive circuitry is configured to apply a voltage to any one of the electrodes in each of the electrode groups. The drive circuitry is disposed in the first substrate and is adapted to pivot each of the mirror faces about the point in space. The device has a sense circuit coupled between each of the electrodes and the drive circuitry, an input/output circuit coupled to the drive circuitry, and a plurality of pads coupled to the input/output circuit.
Many benefits are achieved by way of the present invention over conventional techniques. In a specific embodiment, the invention provides an integrated solution for controlling each of the mirrors on the array using integrated circuit technology. Additionally, the invention can be made using conventional semiconductor technology. In other aspects, the invention reduces a number of possible interconnects, which interface to a controller device, e.g., computer, network switching module. The invention is easy to make and can be used to form highly integrated and large density mirror arrays, e.g., 100, 500, 1000, 5000, 10,000 and greater. The invention also has the ability to sense small variations in capacitance to sense movement of the mirrors. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below.
Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow.